The present invention relates in general to garage doors and in particular to a new and useful spring balanced door which includes arms rigidly connected to opposite edges of a door panel and extending perpendicularly to a plane of the door panel which are connected to biasing means for the door panel.
Overhead doors for buildings which consist of a displaceable panel which is movable toward the interior of the building by means of two lever arms and two lateral vertical tracks, are known in the art. In such doors the panel is normally balanced by counterweights or springs. Depending on the proper choice of the fulcra for the arms, the guidance elements and the balance elements, it is possible to achieve a correct equilibrium of the door panel. Moreover, since the door does not jut out from the building, it does not endanger passers-by. At the same time, it can be opened from inside the building, in particular the garage, even if there is snow in front of the door.
Another advantage of these doors is that the person operating them by hand does not have to stoop in order to open or close them.
Such doors have, however, the disadvantage that when being closed they get very near a dead point position which renders impossible, or at least makes very dangerous, the application of electro-mechanical drives.
Various earler embodiments of garage doors have been illustrated in the present inventor's Argentine Pat. Nos. 87,855 (dated Jan. 8, 1953); 123,046 (dated Aug. 29, 1960); 199,969 (dated Oct. 8, 1974); 203,723 (dated Oct. 15, 1975) and 209,202 (dated Mar. 31, 1977, as well as in his U.S. Pat. No. 3,849,937 (dated Nov. 26, 1974). It should be pointed out that in all these patents, where the door panel is balanced by counterweights or by springs, the inventor has tried to suspend this panel as centrally as possible in order to make easier a calculation of the remaining variables and to avoid having the panel out of balance.